This application claims the benefit of Korean Patent Application No. 2001-8744, filed on Feb. 21, 2001, under 35 U.S.C. xc2xa7119, the entirety of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a system of assembling a wavelength-division multiplexing (WDM) filter assembly for optical amplifier.
2. Description of Related Art
Recent technology development of an information-communication industry makes it possible to transmit large amounts of data over a long distance in a short time. A wavelength-division multiplexing (WDM) has been developed which is a data transmission method that transmits a light signal having several wavelengths through respective optical fiber constituting a cable. The WDM uses the existing cable network but shows such effect as install a new cable network. Also, a WDM filter for use in such a WDM is recently developed.
There are many methods to align the WDM filter. A manual rotational alignment is usually used. An automatic rotational alignment is tried but has some limitations due to material""s tolerances.
The WDM filter assembly includes a filter assembly and a collimator. The filter assembly and the collimator are manufactured in separate process and then assembled. When assembled, an alignment between the filter assembly and the collimator is very important. For example, if the filter assembly is not accurately aligned with the collimator, it is difficult to expect a desirable performance of the WDM filter.
To obtain the desirable performance of the WDM filter, the filter assembly and the collimator are temporally assembled, and then are aligned with each other until a signal having wanted characteristics is output. Thereafter, the filter assembly and the collimator are firmly assembled by an adhesive.
For more detail, in the state that filter assembly and the collimator are temporally assembled, a laser is applied to the collimator. A wavelength that passes through the filter assembly and the collimator is detected, and an operator manually rotates either of the filter assembly and the collimator in consideration of a detected result until a desirable characteristic is detected. When the desirable characteristic is detected, an alignment between the filter assembly and the collimator is completed. Then, the filter assembly and the collimator stick to each other.
In order to overcome problems due to the manually aligning method described above, developed is recently an alignment technique which forcibly grips and rotates the filter assembly by using a gripper comprised of a rubber belt to align with the collimator fixed.
However, such an alignment technique has the following disadvantages: it is difficult to control a tension of the belt when the gripper rotates the filter assembly and a tension is asymmetry in rotational direction. It takes a long time to set the belt around an outer surface of the filter assembly. And since the filter assembly is forcibly rotated in disregard of a manufacturing tolerance of the filter assembly and the collimator, a lens of the collimator may be damaged.
To overcome the problems described above, preferred embodiments of the present invention provide a system of assembling a WDM filter assembly having a short alignment time.
It is another object of the present invention to provide a system of assembling a WDM filter assembly which can prevent parts of the WDM filter assembly from being damaged.
It is a still object of the present invention to provide a system of assembling a WDM filter assembly that can provide an accurate alignment.
In order to achieve the above object, the preferred embodiments of the present invention provide a system of assembling a WDM filter assembly including a filter assembly and a collimator. The system includes a holding means for accepting and holding one of the filter assembly and the collimator, a pivotal means for pivotally moving one which of the filter assembly and the collimator is not held, a detecting means for detecting a signal going through the WDM filter assembly, and a control means for applying a driving signal to drive the pivotal apparatus until the detected siganl is within a predetermined process tollerance, whereby the filter assembly is aligned with the collimator.
The system further includes a signal applying module for applying the signal going through the WDM filter assembly, a measurement means for displaying a characteristic of the detected signal to compare the detected signal with the target sginal, a detecting means support for supporting the detecting means, and a x-y movement means for moving the holding means and the pivotal means in either of a x-axis direction and a y-axis direction, wherein the WDM filter assembly is arranged at a location corresponding to the detecting means by the x-y movement means.
The collimator is held by the holding means. The holding means includes a groove for accepting the collimator and a fixing member for firmly fixing collimator. The holding means is fixed to the x-y movement means. The filter assembly has a hole, and the pivotal means includes a servomotor for providing a rotation, at least one worm gears geared with each other, a pivotal plate for rotating by the rotation transferred by the worm gear, a pin installed on the pivotal plate and fitted into the hole of the filter assembly. The x-y movement means includes a x-axis movement means and a y-axis movement means, the x-axis movement menas moving along a x-axis guide rail, the y-axis movement means moving along the y-axis movement means. The holding means is fixed on the y-axis movement means. The collimator has an optical fiber, and the signal applying module applies the signal going through the WDM filter assembly through the optical fiber. The filter assembly and the collimator are attached by an U.V. curable agent.
The system of assembling the WDM filter assembly has the following advantage: since stiffness of a pin offsets the tolerence between the lens and the filter assembly, an alignment between the filter assembly and the collimator can accurately be performed in a short time, preventing a lens of the collimator from being damaged by using the stiffness of the pin.